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Income Taxes (Summary of Unrecognized Tax Benefits and Temporary Differences) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Unrecognized tax benefits |  |  |
Balance at the beginning of the period | $ 191 | $ 206 | $ 274
Increases related to current year tax positions |  | 4 | 4
Decreases due to tax positions expired | (9) | (19) | (72)
Balance at the end of the period | 182 | 191 | $ 206
Uncertain tax positions, reserved for tax exposure in Europe | 0 | 0 |
Deferred tax assets: |  |  |
Unearned lease revenue | 1,094 | 1,754 |
State taxes | 77 | 1,653 |
Reserves and allowances | 1,187 | 2,531 |
Other accruals | 3,795 | 643 |
Foreign tax credit | 26 | 42 |
Net operating loss carry forward | 39,996 | 29,874 |
Charitable contributions | 38 | 22 |
Total deferred tax assets | 46,213 | 36,519 |
Less: valuation allowance | (652) | (806) |
Net deferred tax assets | 45,561 | 35,713 |
Deferred tax liabilities: |  |  |
Depreciation and impairment on aircraft engines and equipment | (133,453) | (114,347) |
Other deferred tax assets (liabilities) | (2,365) | 437 |
Net deferred tax liabilities | (135,818) | (113,910) |
Other comprehensive income, deferred tax asset | (28) | (83) |
Net deferred tax liabilities | (90,285) | $ (78,280) |
Expired operating loss carryforwards | 5,500 |  |
Valuation allowance of net operating loss | $ 700 |  |
Statutory federal income tax expense (as a percent) | 21.00% | 35.00% |
Provisional amount | $ 43,600 |  |
Federal |  |  |
Deferred tax assets: |  |  |
Alternative minimum tax credit |  | $ 400 |
Deferred tax liabilities: |  |  |
Operating loss carryforwards | 188,300 |  |
Federal | Minimum |  |  |
Deferred tax liabilities: |  |  |
Alternative minimum tax credit period |  | 2 years |
Federal | Maximum |  |  |
Deferred tax liabilities: |  |  |
Alternative minimum tax credit period |  | 4 years |
State |  |  |
Deferred tax liabilities: |  |  |
Operating loss carryforwards | $ 800 |  |

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